Wind power can be generated via a wind-farm wherein wind turbines convert the power in the wind to electricity. Wind farms are created when multiple wind turbines are placed in the same geographic area for the purpose of generating large amounts of electrical power. The power output of each wind turbine varies with wind speed and can be influenced by the wake of an upstream turbine, thus affecting the overall power production of the wind farm.
In a conventional manner, as shown in FIG. 1, an assembled wind turbine 1 includes a tower 2, a nacelle 3 and a rotor including a hub 4 with rotor blades 5. The nacelle 3 is rotatably mounted on the tower 2 around a yawing axle (not shown). A yaw control motor (not shown) is located between the tower 2 and the nacelle 3 to yaw the nacelle based on wind direction. The wind direction is typically measured by use of a wind vane or by use of a sonic wind sensor (not shown). To achieve optimum conversion of wind power into electrical power the rotor axis is aligned with the wind direction.
Wind turbines located downstream from other wind turbines are influenced by the wake of the upstream turbine. As shown in FIG. 2, based on the incoming wind 15a the forward turbine 20 casts a wake 35a onto the downstream turbine 30 thereby influencing the wind 15b impinging on the downstream turbine. As a result, there is less energy in the wind 15b for the downstream turbine 30 to extract, making it less productive, relative to the upstream turbine 20. For small changes in wind direction, there is a functional form to the power production of the downstream turbine 30. It produces the least amount of power when the wind 15a is aligned perfectly with the oriented direction between the turbines 20, 30, and produces more power as the wind direction changes either left or right. The Jensen theory of wake expansion is shown, where wind turbine wakes 35a are known to expand slightly (approximately a 10 degree angle).
In view of the negative influence caused by the wakes of upstream turbines, there is a need in the art for a system and method to increase the power production efficiency of the wind farm by narrowing the influence of such wakes.